Fuzzy logic-based variable impedance control for a bilateral teleoperation system under time delay

In a delayed master-slave teleoperation system, if the slave robot interacts with a delicate and sensitive environment, it is essential to control the slave-environment interactions. Variable impedance control has been proposed as a useful method for this aim in the literature. However, changing the impedance parameters based on the system requirements imposes a complex process in the controller design. To address this issue, we propose a variable impedance control strategy for the slave side, where the impedance variables are changed using fuzzy logic. This is carried out based on the environment destruction threshold—defined based on the contact force and the velocity of the slave robot—and system stability range. The proposed method is simulated in MATLAB’s Simulink considering telesurgery conditions and soft tissue environment under an unknown and varying time delay. Simulation results show that the proposed method maintains the velocity of the slave robot and the environment force in the desired interval and performs better in keeping the environment safe compared to the constant-coefficient impedance control.

Keywords:

teleoperation , Time delay , variable impedance control , absolute stability , Fuzzy logic